Folding knives having mechanical drives for opening a pivotally mounted knife blade are known in the art. One such example is found in U.S. Pat. No. 2,416,277, which discloses a knife opened with a simple rack gear arrangement. A longitudinally disposed actuating member is slidably mounted within the casing and has a handle protruding from one end of the casing. The blade is rotatably mounted at the opposite end of the casing. A plurality of gear teeth formed along one edge of the actuating member engage corresponding gear teeth formed on the pivoting end of the blade. When the handle of the actuating member and the casing are pulled in opposite directions, the actuating member slides within the casing, and the gear teeth on the actuating member engage the gear teeth on the knife blade to pivotally open the blade with respect to the casing.
However, this design suffers a number of disadvantages. First, the actuating member protrudes from the casing at all times, increasing the overall length of what is supposed to be a compact instrument. Also, the action of pulling the casing and the handle of the actuating member in opposite directions requires two hands to operate the knife. Furthermore, with the knife blade pivoted to its opened position, the actuating member protrudes awkwardly from the opposite end of the casing in such a manner as may instruct or impede the use of the knife. Finally, the knife lacks any provision for locking the blade in its closed position to prevent accidental opening.
Another example of a knife opening mechanism is found in U.S. Pat. No. 1,553,985, wherein a bayonet slidably mounted within a rifle forestock is extensible upon actuation of a crank. The pivotally mounted crank has a handle and a plurality of gear teeth disposed to engage a corresponding gear rack found on the shank of the bayonet. Thus, as the crank handle is turned, the teeth on the crank drive the rack on the bayonet to extend or retract the bayonet from the forestock.
Adapting this design to a folding pocket knife would present many of the same disadvantages previously mentioned. The crank handle would protrude awkwardly from the casing, increasing the overall dimensions of the knife. Further, cranking the handle to extend the knife blade would be a two-handed operation. Finally, there is no provision for locking the blade in its closed position to prevent accidental opening.
A different kind of self-opening knife is the so-called "switchblade" knife. These knives have spring-powered blades which rapidly move open at the touch of a release button. The possession of a switchblade knife is unlawful in many jurisdictions.
Accordingly, there is a need to provide an improved knife opening mechanism which can be actuated to extend the knife blade with only one hand, and which does not substantially increase the external dimensions of the knife.